diff --git a/tests/limits_test.cpp b/tests/limits_test.cpp
index 1d48ffe..ed42dbb 100644
--- a/tests/limits_test.cpp
+++ b/tests/limits_test.cpp
@@ -19,9 +19,9 @@
 #include <limits.h>
 
 TEST(limits, macros) {
-#if CHAR_BIT != 8
-#error Insane CHAR_BIT
-#endif
+  ASSERT_EQ(8, CHAR_BIT);
+  ASSERT_EQ(static_cast<int>(sizeof(int)), WORD_BIT);
+  ASSERT_EQ(20, NZERO);
 #if !defined(MB_LEN_MAX)
 #error MB_LEN_MAX
 #endif
diff --git a/tests/unistd_test.cpp b/tests/unistd_test.cpp
index ced0315..81c6d92 100644
--- a/tests/unistd_test.cpp
+++ b/tests/unistd_test.cpp
@@ -686,104 +686,131 @@
   ASSERT_TRUE(rc > 0 && powerof2(rc));
 }
 
-
-TEST(UNISTD_TEST, _POSIX_macros_smoke) {
+TEST(UNISTD_TEST, _POSIX_constants) {
   // Make a tight verification of _POSIX_* / _POSIX2_* / _XOPEN_* macros, to prevent change by mistake.
   // Verify according to POSIX.1-2008.
   EXPECT_EQ(200809L, _POSIX_VERSION);
 
+  EXPECT_EQ(2, _POSIX_AIO_LISTIO_MAX);
+  EXPECT_EQ(1, _POSIX_AIO_MAX);
+  EXPECT_EQ(4096, _POSIX_ARG_MAX);
+  EXPECT_EQ(25, _POSIX_CHILD_MAX);
+  EXPECT_EQ(20000000, _POSIX_CLOCKRES_MIN);
+  EXPECT_EQ(32, _POSIX_DELAYTIMER_MAX);
+  EXPECT_EQ(255, _POSIX_HOST_NAME_MAX);
+  EXPECT_EQ(8, _POSIX_LINK_MAX);
+  EXPECT_EQ(9, _POSIX_LOGIN_NAME_MAX);
+  EXPECT_EQ(255, _POSIX_MAX_CANON);
+  EXPECT_EQ(255, _POSIX_MAX_INPUT);
+  EXPECT_EQ(8, _POSIX_MQ_OPEN_MAX);
+  EXPECT_EQ(32, _POSIX_MQ_PRIO_MAX);
+  EXPECT_EQ(14, _POSIX_NAME_MAX);
+  EXPECT_EQ(8, _POSIX_NGROUPS_MAX);
+  EXPECT_EQ(20, _POSIX_OPEN_MAX);
+  EXPECT_EQ(256, _POSIX_PATH_MAX);
+  EXPECT_EQ(512, _POSIX_PIPE_BUF);
+  EXPECT_EQ(255, _POSIX_RE_DUP_MAX);
+  EXPECT_EQ(8, _POSIX_RTSIG_MAX);
+  EXPECT_EQ(256, _POSIX_SEM_NSEMS_MAX);
+  EXPECT_EQ(32767, _POSIX_SEM_VALUE_MAX);
+  EXPECT_EQ(32, _POSIX_SIGQUEUE_MAX);
+  EXPECT_EQ(32767, _POSIX_SSIZE_MAX);
+  EXPECT_EQ(8, _POSIX_STREAM_MAX);
+#if !defined(__GLIBC__)
+  EXPECT_EQ(4, _POSIX_SS_REPL_MAX);
+#endif
+  EXPECT_EQ(255, _POSIX_SYMLINK_MAX);
+  EXPECT_EQ(8, _POSIX_SYMLOOP_MAX);
+  EXPECT_EQ(4, _POSIX_THREAD_DESTRUCTOR_ITERATIONS);
+  EXPECT_EQ(128, _POSIX_THREAD_KEYS_MAX);
+  EXPECT_EQ(64, _POSIX_THREAD_THREADS_MAX);
+  EXPECT_EQ(32, _POSIX_TIMER_MAX);
+#if !defined(__GLIBC__)
+  EXPECT_EQ(30, _POSIX_TRACE_EVENT_NAME_MAX);
+  EXPECT_EQ(8, _POSIX_TRACE_NAME_MAX);
+  EXPECT_EQ(8, _POSIX_TRACE_SYS_MAX);
+  EXPECT_EQ(32, _POSIX_TRACE_USER_EVENT_MAX);
+#endif
+  EXPECT_EQ(9, _POSIX_TTY_NAME_MAX);
+  EXPECT_EQ(6, _POSIX_TZNAME_MAX);
+  EXPECT_EQ(99, _POSIX2_BC_BASE_MAX);
+  EXPECT_EQ(2048, _POSIX2_BC_DIM_MAX);
+  EXPECT_EQ(99, _POSIX2_BC_SCALE_MAX);
+  EXPECT_EQ(1000, _POSIX2_BC_STRING_MAX);
+  EXPECT_EQ(14, _POSIX2_CHARCLASS_NAME_MAX);
+  EXPECT_EQ(2, _POSIX2_COLL_WEIGHTS_MAX);
+  EXPECT_EQ(32, _POSIX2_EXPR_NEST_MAX);
+  EXPECT_EQ(2048, _POSIX2_LINE_MAX);
+  EXPECT_EQ(255, _POSIX2_RE_DUP_MAX);
+
+  EXPECT_EQ(16, _XOPEN_IOV_MAX);
+#if !defined(__GLIBC__)
+  EXPECT_EQ(255, _XOPEN_NAME_MAX);
+  EXPECT_EQ(1024, _XOPEN_PATH_MAX);
+#endif
+}
+
+TEST(UNISTD_TEST, _POSIX_options) {
   EXPECT_EQ(_POSIX_VERSION, _POSIX_ADVISORY_INFO);
-  EXPECT_GT(_POSIX_AIO_LISTIO_MAX, 0);
-  EXPECT_GT(_POSIX_AIO_MAX, 0);
-  EXPECT_GT(_POSIX_ARG_MAX, 0);
   EXPECT_GT(_POSIX_BARRIERS, 0);
   EXPECT_GT(_POSIX_SPIN_LOCKS, 0);
-  EXPECT_GT(_POSIX_CHILD_MAX, 0);
   EXPECT_NE(_POSIX_CHOWN_RESTRICTED, -1);
   EXPECT_EQ(_POSIX_VERSION, _POSIX_CLOCK_SELECTION);
+#if !defined(__GLIBC__) // glibc supports ancient kernels.
   EXPECT_EQ(_POSIX_VERSION, _POSIX_CPUTIME);
-  EXPECT_GT(_POSIX_DELAYTIMER_MAX, 0);
+#endif
   EXPECT_EQ(_POSIX_VERSION, _POSIX_FSYNC);
-  EXPECT_GT(_POSIX_HOST_NAME_MAX, 0);
   EXPECT_EQ(_POSIX_VERSION, _POSIX_IPV6);
   EXPECT_GT(_POSIX_JOB_CONTROL, 0);
-  EXPECT_GT(_POSIX_LINK_MAX, 0);
-  EXPECT_GT(_POSIX_LOGIN_NAME_MAX, 0);
   EXPECT_EQ(_POSIX_VERSION, _POSIX_MAPPED_FILES);
-  EXPECT_GT(_POSIX_MAX_CANON, 0);
-  EXPECT_GT(_POSIX_MAX_INPUT, 0);
   EXPECT_EQ(_POSIX_VERSION, _POSIX_MEMLOCK);
   EXPECT_EQ(_POSIX_VERSION, _POSIX_MEMLOCK_RANGE);
   EXPECT_EQ(_POSIX_VERSION, _POSIX_MEMORY_PROTECTION);
+#if !defined(__GLIBC__) // glibc supports ancient kernels.
   EXPECT_EQ(_POSIX_VERSION, _POSIX_MONOTONIC_CLOCK);
-  EXPECT_GT(_POSIX_MQ_OPEN_MAX, 0);
-  EXPECT_GT(_POSIX_MQ_PRIO_MAX, 0);
-  EXPECT_GT(_POSIX_NAME_MAX, 0);
-  EXPECT_GT(_POSIX_NGROUPS_MAX, 0);
+#endif
   EXPECT_GT(_POSIX_NO_TRUNC, 0);
-  EXPECT_GT(_POSIX_OPEN_MAX, 0);
-  EXPECT_GT(_POSIX_PATH_MAX, 0);
-  EXPECT_GT(_POSIX_PIPE_BUF, 0);
   EXPECT_EQ(_POSIX_VERSION, _POSIX_PRIORITY_SCHEDULING);
   EXPECT_EQ(_POSIX_VERSION, _POSIX_RAW_SOCKETS);
   EXPECT_EQ(_POSIX_VERSION, _POSIX_READER_WRITER_LOCKS);
   EXPECT_EQ(_POSIX_VERSION, _POSIX_REALTIME_SIGNALS);
   EXPECT_GT(_POSIX_REGEXP, 0);
-  EXPECT_GT(_POSIX_RE_DUP_MAX, 0);
   EXPECT_GT(_POSIX_SAVED_IDS, 0);
   EXPECT_EQ(_POSIX_VERSION, _POSIX_SEMAPHORES);
-  EXPECT_GT(_POSIX_SEM_NSEMS_MAX, 0);
-  EXPECT_GT(_POSIX_SEM_VALUE_MAX, 0);
   EXPECT_GT(_POSIX_SHELL, 0);
-  EXPECT_GT(_POSIX_SIGQUEUE_MAX, 0);
   EXPECT_EQ(_POSIX_VERSION, _POSIX_SPAWN);
-  EXPECT_EQ(_POSIX_VERSION, _POSIX_SPORADIC_SERVER);
-  EXPECT_GT(_POSIX_SSIZE_MAX, 0);
-  EXPECT_GT(_POSIX_STREAM_MAX, 0);
-  EXPECT_GT(_POSIX_SYMLINK_MAX, 0);
-  EXPECT_GT(_POSIX_SYMLOOP_MAX, 0);
+  EXPECT_EQ(-1, _POSIX_SPORADIC_SERVER);
   EXPECT_EQ(_POSIX_VERSION, _POSIX_SYNCHRONIZED_IO);
   EXPECT_EQ(_POSIX_VERSION, _POSIX_THREADS);
   EXPECT_EQ(_POSIX_VERSION, _POSIX_THREAD_ATTR_STACKADDR);
   EXPECT_EQ(_POSIX_VERSION, _POSIX_THREAD_ATTR_STACKSIZE);
+#if !defined(__GLIBC__) // glibc supports ancient kernels.
   EXPECT_EQ(_POSIX_VERSION, _POSIX_THREAD_CPUTIME);
-  EXPECT_GT(_POSIX_THREAD_DESTRUCTOR_ITERATIONS, 0);
-  EXPECT_EQ(_POSIX_THREAD_KEYS_MAX, 128);
+#endif
   EXPECT_EQ(_POSIX_VERSION, _POSIX_THREAD_PRIORITY_SCHEDULING);
-  EXPECT_EQ(-1, _POSIX_THREAD_PRIO_INHERIT);
-  EXPECT_EQ(-1, _POSIX_THREAD_PRIO_PROTECT);
   EXPECT_EQ(_POSIX_VERSION, _POSIX_THREAD_PROCESS_SHARED);
   EXPECT_EQ(-1, _POSIX_THREAD_ROBUST_PRIO_PROTECT);
   EXPECT_EQ(_POSIX_VERSION, _POSIX_THREAD_SAFE_FUNCTIONS);
-  EXPECT_EQ(_POSIX_VERSION, _POSIX_THREAD_SPORADIC_SERVER);
-  EXPECT_GT(_POSIX_THREAD_THREADS_MAX, 0);
+  EXPECT_EQ(-1, _POSIX_THREAD_SPORADIC_SERVER);
   EXPECT_EQ(_POSIX_VERSION, _POSIX_TIMEOUTS);
   EXPECT_EQ(_POSIX_VERSION, _POSIX_TIMERS);
-  EXPECT_GT(_POSIX_TIMER_MAX, 0);
   EXPECT_EQ(-1, _POSIX_TRACE);
   EXPECT_EQ(-1, _POSIX_TRACE_EVENT_FILTER);
   EXPECT_EQ(-1, _POSIX_TRACE_INHERIT);
   EXPECT_EQ(-1, _POSIX_TRACE_LOG);
-  EXPECT_GT(_POSIX_TTY_NAME_MAX, 0);
   EXPECT_EQ(-1, _POSIX_TYPED_MEMORY_OBJECTS);
-  EXPECT_GT(_POSIX_TZNAME_MAX, 0);
   EXPECT_NE(-1, _POSIX_VDISABLE);
 
   EXPECT_EQ(_POSIX_VERSION, _POSIX2_VERSION);
-  EXPECT_GT(_POSIX2_BC_BASE_MAX, 0);
-  EXPECT_GT(_POSIX2_BC_DIM_MAX, 0);
-  EXPECT_GT(_POSIX2_BC_SCALE_MAX, 0);
-  EXPECT_GT(_POSIX2_BC_STRING_MAX, 0);
-  EXPECT_GT(_POSIX2_CHARCLASS_NAME_MAX, 0);
-  EXPECT_GT(_POSIX2_COLL_WEIGHTS_MAX, 0);
   EXPECT_EQ(_POSIX_VERSION, _POSIX2_C_BIND);
-  EXPECT_GT(_POSIX2_EXPR_NEST_MAX, 0);
-  EXPECT_GT(_POSIX2_LINE_MAX, 0);
-  EXPECT_GT(_POSIX2_RE_DUP_MAX, 0);
+  EXPECT_EQ(_POSIX_VERSION, _POSIX2_CHAR_TERM);
 
   EXPECT_EQ(700, _XOPEN_VERSION);
-  EXPECT_GT(_XOPEN_IOV_MAX, 0);
-  EXPECT_GT(_XOPEN_UNIX, 0);
+  EXPECT_EQ(1, _XOPEN_ENH_I18N);
+  EXPECT_EQ(1, _XOPEN_REALTIME);
+  EXPECT_EQ(1, _XOPEN_REALTIME_THREADS);
+  EXPECT_EQ(1, _XOPEN_SHM);
+  EXPECT_EQ(1, _XOPEN_UNIX);
 
 #if defined(__BIONIC__)
   // These tests only pass on bionic, as bionic and glibc has different support on these macros.
@@ -792,21 +819,20 @@
   EXPECT_EQ(-1, _POSIX_MESSAGE_PASSING);
   EXPECT_EQ(-1, _POSIX_PRIORITIZED_IO);
   EXPECT_EQ(-1, _POSIX_SHARED_MEMORY_OBJECTS);
+  EXPECT_EQ(-1, _POSIX_THREAD_PRIO_INHERIT);
+  EXPECT_EQ(-1, _POSIX_THREAD_PRIO_PROTECT);
   EXPECT_EQ(-1, _POSIX_THREAD_ROBUST_PRIO_INHERIT);
 
-  EXPECT_EQ(-1, _POSIX2_CHAR_TERM);
   EXPECT_EQ(-1, _POSIX2_C_DEV);
+  EXPECT_EQ(-1, _POSIX2_FORT_DEV);
+  EXPECT_EQ(-1, _POSIX2_FORT_RUN);
   EXPECT_EQ(-1, _POSIX2_LOCALEDEF);
   EXPECT_EQ(-1, _POSIX2_SW_DEV);
   EXPECT_EQ(-1, _POSIX2_UPE);
 
-  EXPECT_EQ(-1, _XOPEN_ENH_I18N);
   EXPECT_EQ(-1, _XOPEN_CRYPT);
   EXPECT_EQ(-1, _XOPEN_LEGACY);
-  EXPECT_EQ(-1, _XOPEN_REALTIME);
-  EXPECT_EQ(-1, _XOPEN_REALTIME_THREADS);
-  EXPECT_EQ(-1, _XOPEN_SHM);
-
+  EXPECT_EQ(-1, _XOPEN_STREAMS);
 #endif // defined(__BIONIC__)
 }
 
@@ -916,11 +942,11 @@
   VERIFY_SYSCONF_POSITIVE(_SC_REGEXP);
   VERIFY_SYSCONF_POSITIVE(_SC_SHELL);
   VERIFY_SYSCONF_POSIX_VERSION(_SC_SPAWN);
-  VERIFY_SYSCONF_POSIX_VERSION(_SC_SPORADIC_SERVER);
+  VERIFY_SYSCONF_UNSUPPORTED(_SC_SPORADIC_SERVER);
   VERIFY_SYSCONF_POSITIVE(_SC_SYMLOOP_MAX);
   VERIFY_SYSCONF_POSIX_VERSION(_SC_THREAD_CPUTIME);
   VERIFY_SYSCONF_POSIX_VERSION(_SC_THREAD_PROCESS_SHARED);
-  VERIFY_SYSCONF_POSIX_VERSION(_SC_THREAD_SPORADIC_SERVER);
+  VERIFY_SYSCONF_UNSUPPORTED(_SC_THREAD_SPORADIC_SERVER);
   VERIFY_SYSCONF_POSIX_VERSION(_SC_TIMEOUTS);
   VERIFY_SYSCONF_UNSUPPORTED(_SC_TRACE);
   VERIFY_SYSCONF_UNSUPPORTED(_SC_TRACE_EVENT_FILTER);